Membrane-electrode assembly, electrolytic cell employing the same, electrolytic-water sprayer, and method of sterilization

ABSTRACT

The present invention provides a membrane-electrode assembly which comprises: at least one rod-form or tubular electrode; a tubular diaphragm disposed around the periphery of the electrode; and a wire-form counter electrode disposed around the periphery of the diaphragm, the diaphragm being fixed to the rod-form or tubular electrode with the wire-form counter electrode to thereby form an electrode chamber having a gas/liquid passage between the diaphragm and the rod-form or tubular electrode.

FIELD OF THE INVENTION

The present invention relates to a membrane-electrode assembly foryielding electrolytic water to be used for sterilization, cleaning,etc., an electrolytic cell employing the assembly, an electrolytic-watersprayer including any of the electrolytic cell, and a method ofsterilization using these.

BACKGROUND OF THE INVENTION Bactericide/Disinfectant Solution:

Chlorine compound bactericides such as sodium hypochlorite, calciumhypochlorite, and sodium dichloroisocyanurate have been extensively usedas bactericides/disinfectants in a wide range of environments. Of these,hypochlorites including sodium hypochlorite are in general use from thestandpoints of cost and effect. However, many proposals have been madefor attaining improvements in the bactericidal/disinfectant effectthereof which are required in various fields including the clinicalfield and the food industry (see, for example, JP-A-2001-253803,JP-A-2001-342496, and JP-A-2002-145710).

Usually, such bactericides/disinfectants are prepared by adding therespective ingredients for constituting the composition to water or bymixing aqueous solutions containing the respective ingredients.

Use of Electrolytic Water as Substitute:

However, the use of chlorine compound bactericides in large amountsarouses troubles. For example, in factories and retail stores where foodmaterials are handled in large quantities, cleaning with a sodiumhypochlorite solution having a concentration exceeding 100 ppm isconducted. This cleaning, however, is regarded as problematic because itnot only spoils the flavors of the food materials but also arouses ahazard (increase in THM).

Mainly for the purpose of eliminating those problems, investigationshave been diligently made on the usefulness of electrolytic water, i.e.,water yielded by electrolysis, in the agricultural, food, clinical, andother fields. The substitution of electrolytic water or ozonized wateris proceeding mainly in Japan. Electrical energy, which is a cleanenergy, can be utilized to synthesize hydrogen, oxygen, ozone, hydrogenperoxide, etc. through chemical reactions on electrode surfaces whileregulating the reactions. It is known that oxidation reactionsespecially on the anode yield oxidizing agents effective in watertreatments (effective chlorine and peroxides such as ozone) and furthergenerate active species such as OH radicals in some cases (KyōsanseiDenkaisui No Kiso Chishiki (Fundamental Knowledge of Strongly AcidicElectrolytic Water), Ohm-sha, Ltd.).

Attention is being directed to the excellent bactericidal/disinfectantactivity of electrolytic water, and investigations are being made on theuse of the water in clinical activities and in the home. Examples of theuses thereof which are being investigated include thesterilization/disinfection of diseased parts, incised parts,percutaneous openings for stationary catheters, etc. and thesterilization/disinfection of domestic utensils or articles, such askitchen utensils, baby articles, and furniture, and house equipmentssuch as the toilet facilities and bathtub. Such electrolytic water isobtained by electrolyzing water (water to be electrolyzed) to which asolute that generates ions upon dissolution, e.g., sodium chloride, hasbeen added optionally together with an acid for pH regulation.

Kinds of Electrolytic Water:

Besides being used as a food additive, electrolytic water is usable alsoin other applications. In an electrolytic cell containing water only,the following anode reaction proceeds to evolve oxygen according toformula (1). However, depending on the catalyst and electrolysisconditions, ozone is yielded according to formula (2) and ozonized watercontaining the ozone dissolved therein can be synthesized.

2H₂O=O₂+4H⁺+4e  (1)

3H₂O=O₃+6H⁺+6e  (2)

In the case where the water contains hydrochloric acid or chloride ionsadded thereto, hypochlorous acid is yielded according to formulae (3)and (4). In the case where the water contains sulfuric acid, thereaction represented by formula (5) proceeds to yield persulfuric acid.

Cl⁻=Cl₂+2e  (3)

Cl₂+H₂O=HCl+HClO  (4)

2SO₄ ²⁻=S₂O₆ ²⁻+2e  (5)

When carbonate ions are present, the reaction represented by formula (6)proceeds to yield percarbonic acid.

2CO₃ ²⁻=C₂O₆ ²⁻+2e  (6)

Through cathode reactions, it is possible to synthesize hydrogenouswater, which is water containing excess hydrogen dissolved therein,alkali ion waters and the like according to formulae (7) and (8).

2H⁺+2e=H₂  (7)

2H₂O+2e=H₂+2OH⁻  (8)

Furthermore, hydrogen peroxide or the like can also be synthesized.

As shown above, electrolytic water containing two or more peroxides canbe produced with electrolytes suitably selected, besides the acid waterswhich have been approved as food additives.

Features of Electrolytic Water: (reference: Mizu No Tokusei To AtarashiiRiyō Gijutsu (Characteristics of Water And Novel ApplicationTechnology), 2004, NTS Inc.)

There are the following three kinds of electrolytic water which havebeen approved as food additives.

a) Weakly alkaline electrolytic hypochlorite water (additive name,electrolytic sodium hypochlorite water; 20-200 ppm; pH>7.5; yielded from0.2-2% aqueous sodium chloride solution using no diaphragm)

b) Slightly acid electrolytic water (additive name, slightly acidhypochlorous acid water; 10-30 ppm; pH=5-6.5; yielded from 2-6%hydrochloric acid using no diaphragm)

c) Strongly acid electrolytic water (additive name, strongly acidhypochlorous acid water; 20-60 ppm; pH<2.7; yielded as anolyte waterfrom 0.2% or lower aqueous sodium chloride solution in diaphragm typecell)

The acid waters among those kinds of electrolytic water have, forexample, the following merits.

(1) The acid waters are superior in safety because THMs are less apt togenerate under acid conditions.

(2) Resistant bacteria are less apt to generate and on-site managementis easy.

(3) The waters can be used for treatment in combination with thealkaline electrolytic water.

(4) The waters can be utilized like tap water and impart no remainingodor to the hands or fingers.

(5) Use of the waters just before suffices (sterilization time isshort).

In the conventional treatment with sodium hypochlorite solutions, use ofthis chemical having a concentration up to 200 ppm as a food additivehas been approved. However, the chemical spoils the flavor and has aresidual tendency. In contrast, the electrolytic water of those kindshas a high bactericidal effect even in a low concentration and isbeneficial, although use thereof necessitates an initial investment inthe apparatus.

Features of Ozonized Water:

The long-term use of hypochlorites has yielded bacteria resistant tothese chemicals, and there is a doubt about the bactericidal effectthereof. On the other hand, ozonized water has been placed on foodadditive lists and has gained approval of FDA (Food and DrugAdministrations) of U.S.A. (2001) for use as a bactericide in foodstorage/production steps. Ozonized water has already come into manypractical uses for sterilization in food factories and the sterilizationof foods themselves. Recently, attention is focused on the fact thatozonized water is equal or superior in effect to sterilizing watersheretofore in use also in clinical fields such as dermatology,opthalmology, and dentistry and is effective in reducing the burden tobe imposed on the living body.

Ozonized water has, for example, the following merits.

(1) The bactericidal effect of ozone (OH radicals) is based on theoxidative destruction of cell walls and this indiscriminate activity isthought not to generate resistant bacteria.

(2) Ozone does not have a residual tendency.

When ozonized water is used in combination with an oxidizing agenthaving a residual tendency (e.g., a hypochlorite, persulfate, orpercarbonate) according to need, a more effective sterilizationtreatment is possible.

Conventional Process for Producing Ozonized Water:

ozonized water has conventionally been produced generally with adischarge type ozone gas generator. Ozonized water having aconcentration of several parts per million parts can be easily producedby the process, and is being utilized in the fields of waterpurification treatment and food cleaning. However, the apparatus hasbeen unsuitable for use as a handy ozonized-water production apparatushaving excellent instant-response characteristics and yieldinghigh-concentration ozonized water, for the following reasons.

(1) The ozonized-water production necessitates two steps, i.e., firstgenerating ozone as a gas and then dissolving the gas in water.

(2) The ozonized water has a lower concentration than that produced bythe electrolytic process which will be described later and, hence, thewater should be produced through high-pressure injection into water anddissolution therein.

(3) The power source fox ozone generation has a high voltage and a highfrequency, making it difficult to attain a size reduction.

(4) In the ozonized-water production apparatus based on a discharged, acertain time period (stand-by time of several minutes) is required forthe ozone gas generation ability to become stable and it is difficult toinstantaneously prepare ozonized water having a certain concentration.

Electrolytic Ozone Production Process:

The electrolytic process is inferior to the discharge process inelectric power consumption rate. However, a feature of the electrolyticprocess resides in that high-concentration ozone gas and ozonized watercan be easily obtained. The electrolytic process is hence in general usein special fields such as, e.g., the cleaning of electronic parts. Sincea direct-current low-voltage power source is employed because of theprinciple of the process, the apparatus is excellent in instant-responsecharacteristics and safety and is expected to be used as a small ozonegas generator or a small ozonized-water production apparatus. Accordingto applications, a driving mode can be selected from battery driving,power-generator driving, and AC-DC conversion driving.

For efficiently generating ozone gas, it is indispensable to select aproper catalyst and electrolyte. Known electrode materials include noblemetals such as platinum, α-lead dioxide, β-lead dioxide, glassy carbonimpregnated with a fluorocarbon, and diamond. As an electrolyte, use hasbeen made of an aqueous solution containing sulfuric acid, phosphoricacid, fluorinated groups, or the like. However, these electrolytes havepoor handleability and are not in extensive use. A water electrolysiscell which employs a solid polymer electrolyte as a diaphragm and inwhich pure water is used as a raw material is easy to manage in thatrespect and is in general use (J. Electrochem. Soc., 132, 367 (1985)).When lead dioxide, which has been employed as a catalyst, is used, ozonegas having a concentration as high as 12% or above is obtained.

In the system called a direct synthesis system, the solution locatedaround an electrode is caused to flow at a sufficient velocity tothereby take out the ozone as ozonized water before gasifying(JP-A-8-134677). Furthermore, in the case where raw water other thanpure water is supplied to the electrolytic system, the activity of thenoble-metal electrode catalyst itself is influenced by the quality ofthe water. Care should hence be given to the fact that electrolyticperformances such as life and efficiency fluctuate. JP-A-9-268395discloses that conductive diamond is useful as an electrode forproducing functional water (containing ozone).

Development of Small Apparatus:

Portable or small electrolytic-water production/ejection apparatus havebeen proposed in order to more easily conduct sterilization/disinfectionor the like in clinical activities or in the home (see patent documents1 to 3). Such small apparatus may be extensively used for thedeodorization, sterilization, or bleaching of indoor facilities,water-related facilities, tableware, garments, etc. in the home or forbusiness purposes or for the sterilization or disinfection of the humanbody, e.g., the hands or fingers, etc.

Patent Document 1: JP-A-2000-79393

Patent Document 2: JP-A-2000-197889

Patent Document 3: JP-A-2001-276826

Besides those, the following are known: JP-A-2004-129954 (apparatushaving a device which generates power necessary for electrolysis);JP-A-2004-130263 (apparatus in which the proportion of the capacity ofthe piston to the volume, sectional area, etc. of the cell cylinder partis a specific value); JP-A-2004-130264 (apparatus in which raw water forelectrolysis comprising a pH regulator, surfactant, chlorine compound,and water is used to obtain electrolytic water having a pH of 3-8.5);JP-A-2004-130265 (the electrolytic water according to JP-A-2004-130264is used in a foamed state); JP-A-2004-130266 (the direction of voltageapplication to the electrodes is changed alternately); JP-A-2004-148108(the voltage to be applied to the electrodes is variable);JP-A-2004-148109 (apparatus having electrodes in a suction passage);JP-A-2003-93479, JP-A-2003-266073, and JP-A-2002-346564 (separation typehaving a cylindrical electrode in a spraying part); and JP-A-2001-47048(gun type prevented from being clogged during non-spraying period andequipped with a motor).

Known techniques intended to synthesize ozonized water include thefollowing. JP-A-2000-169989 discloses a small electrolytic ozonegenerator which has a structure including an assembly composed of asolid cylindrical shaft and, wound on the shaft, a metal-gauze-likeanode (platinum), an ion-exchange membrane, and a metal-gauze-likecathode and disposed in a water channel and in which the shaft has athin groove formed therein. JP-A-2001-198574 discloses a module forconnection to piping which includes a solid cylindrical shaft and, fixedto the shaft, a porous anode, a solid polymer electrolyte (ion-exchangemembrane), and a porous cathode and has a drain line capable ofseparately discharging the ozonized water to be synthesized at the anodeand the hydrogen/hydrogen gas to be synthesized at the cathode.JP-A-2002-143851 discloses a method of water treatment with adouble-pipe structure including a supporting cylindrical member having athrough-hole and, wound on the cylindrical member, a cathode, amembrane, and an anode. In this method, hard-water components can beinhibited from depositing from tap water as raw water by passing adilute aqueous solution of sodium chloride through the cylinder servingas a cathode chamber, and an ultraviolet treatment can also be conductedsimultaneously. JP-A-2004-60010 and JP-A-2004-60011 disclose anozonized-water production apparatus which is capable of separating acatholyte with an electrolytic cell equal to that described inJP-A-2000-169989 and of measuring the concentration of ozone with anelectromotive-force measuring device disposed in the channel.JP-A-2006-346203 discloses use of conductive diamond as an electrodeand, in particular, discloses an electrolytic cell including a rod-formconductive-diamond electrode, a strip-form diaphragm member disposedaround the electrode, and a wire-form counter electrode disposed on thediaphragm member. Furthermore, JP-A-2007-136356 discloses a structureincluding a cylindrical core member having grooves extending in thecylinder direction and, wound on the core member in the following order,a cathode, a membrane, and an anode.

SUMMARY OF THE INVENTION

Conventional small electrode assemblies and electrolytic cells employingthe assemblies have had the following problems.

(1) Although use of an ion-exchange membrane or the like improves ionicconductivity and this is expected to increase electrolysis reactionefficiency, it has been difficult to join the membrane or the like withthe electrodes.

(2) The membrane usually is nonporous and is used usually in combinationwith porous electrodes for facilitating the feeling of an electrolyticsolution and removal of products. The shape of the electrode assembly ishence complicated.

(3) When the assembly is to be attached to an apparatus, the pipingmembranes are frequently cylindrical and, hence, the electrodespreferably have a shape suitable for the piping members, i.e., arod-form or cylindrical shape. It has been necessary to employ anapparatus suitable for that shape.

(4) Although a platinum catalyst is excellent in the property ofaccelerating ozone generation, it is unstable and apt to be influencedby the raw water. There are cases where ozonized water having aconcentration of several parts per million, which enables short-timesterilization, cannot be synthesized when tap water is used as it is.

(5) In yielding ozonized water, the hydrogen which has generated at thecounter electrode is separated to increase partial pressure and thisinevitably results in an increase in solute concentration. However,there has been no cell having a structure suitable for that.

If those problems are overcome, it is expected that the use ofelectrolytic water in the home, hospitals, nursing care facilities, etc.expands further.

An object of the invention is to provide a membrane-electrode assemblywith which many of those problems can be eliminated and which can beeasily produced and bring about high performance. Another object of theinvention is to provide an electrolytic cell and an electrolytic-watersprayer, each employing the assembly, and a method of sterilization. Theelectrolytic-water sprayer of the invention electrolyzes a raw aqueoussolution, and the electrolytic water thus yielded can be immediatelyutilized.

The invention first provides a membrane-electrode assembly whichcomprises:

at least one rod-form or tubular electrode;

a tubular diaphragm, preferably ion-exchange membrane, disposed aroundthe periphery of the electrode; and

a wire-form counter electrode disposed around the periphery of thediaphragm,

the diaphragm being fixed to the rod-form or tubular electrode with thewire-form counter electrode to thereby form an electrode chamber havinga gas/liquid passage between the diaphragm and the rod-form or tubularelectrode.

The invention secondly provides a membrane-electrode assembly whichcomprises

at least one rod-form or tubular electrode;

a tubular diaphragm disposed around the periphery of the electrode; and

a porous counter electrode disposed around the periphery of thediaphragm,

the diaphragm being fixed to the rod-form or tubular electrode with theporous counter electrode to thereby form an electrode chamber having agas/liquid passage between the diaphragm and the rod-form or tubularelectrode.

The invention thirdly provides a membrane-electrode assembly whichcomprises:

at least one rod-form or tubular electrode having a recessed part formedtherein;

a tubular diaphragm disposed around the periphery of the electrode so asto form an electrode chamber having a gas/liquid passage between thediaphragm and the electrode; and

a platy counter electrode disposed around the periphery of thediaphragm.

According to the invention, an electrolytic cell and anelectrolytic-water sprayer each having the membrane-electrode assemblycan be constituted. The electrolytic-water sprayer can be used to yieldelectrolytic water and eject the electrolytic water to a substance tosterilize it.

The invention will be explained below in detail.

The membrane-electrode assembly of the invention is characterized bybeing produced by disposing a tubular diaphragm, e.g., an ion-exchangemembrane, around the periphery of a rod-form or tubular electrode,usually an anode (hereinafter referred to also as rod anode), disposinga wire-form or porous counter electrode, usually a wire-form or porouscathode, around the periphery of the membrane, fixing those members withthe cathode so that the membrane is in contact with at least part of theanode and that the membrane is in contact with at least part of thecathode, and forming an anode chamber having a gas/liquid passagebetween the membrane and the anode and preferably among a plurality ofanodes.

In the invention, an anode chamber separated from a cathode chamber by adiaphragm is formed to constitute an appropriate gas/liquid passage. Bychanging a water feed rate and current value, the concentration of anelectrolytically yielded species in the electrolytic water can beregulated to a desired value.

In the following explanations, the rod electrode and the counterelectrode are used as an anode and a cathode, respectively. In theinvention, however, the rod electrode and the counter electrode may beconversely used as a cathode and an anode, respectively.

This membrane-electrode assembly can have a constitution including a rodanode, a sheet-form membrane disposed, in a tube-forming manner, aroundthe periphery of the anode, and a wire cathode spirally wound thereon atan appropriate pitch. In this constitution, not only the rod anode,membrane, and wire cathode can be kept in partial contact with eachother but also an anode chamber through which the liquid and the gasgenerated can move spirally can be formed between the rod anode and themembrane or among a plurality of rod anodes.

A membrane-electrode assembly having an ideal passage is obtained bysuitably selecting the diameter and number of the rod anode, diameter ofthe tubular membrane, and material, thickness, and winding pitch of thewire cathode. In particular, by spirally winding the wire cathode at apitch of 1-10 mm, an assembly having a suitable structure is obtained.It is especially preferred that the anode should be diamond, becausethis assembly can efficiently generate ozone, etc.

This membrane-electrode assembly can be used to constitute anelectrolytic cell which includes a tube fixed to at least one of theopenings of the anode chamber and one or two feeder terminals connectedto the anode and/or the cathode.

Furthermore, by fixing a tube to the two openings of the anode chamberformed between the anode and the diaphragm and fixing the resultantmember in a second tube having at least two openings, a cathode chambercan be formed between the cathode and the diaphragm. One or two feederterminals are connected to the anode and/or cathode. Thus, anelectrolytic cell can be constituted in which electrolysis is conductedwhile feeding raw water to one of the openings of the anode chamber andfeeding raw water also to one of the openings of the cathode chamberaccording to need. Since the diaphragm has been deformed so as tospirally form the anode chamber between the diaphragm and the anode, thecathode chamber also has been spirally formed. Because of this, the gasand liquid present near the cathode in the cathode chamber can be causedto flow spirally. In this cell, acid water and alkaline water can besimultaneously synthesized in the anode chamber and the cathode chamber,respectively.

When the raw water is passed through the electrolytic cell and a voltageis applied to the cell, then the raw water comes into contact with therod electrode and counter electrode in the electrolytic cell and iselectrolyzed to yield electrolytic water.

This electrolytic cell is mounted in an electrolytic-water ejectionapparatus including a vessel containing raw water and a head. When theraw water is sucked up and passed through the tube and a voltage isapplied to the electrolytic cell, then the raw water comes into contactwith the rod anode and the cathode in the electrolytic cell and iselectrolyzed to yield electrolytic water. This electrolytic water isdischarged outside in an atomized or liquid state through the nozzle ofthe head optionally with a power assist such as, e.g., a pump.

Alternatively, the electrolytic cell may be directly connected to awater supply line. When raw water is fed from the water supply line tothe anode chamber or cathode chamber and electrolyzed while being fed,then the same active electrolytic water is yielded.

In those electrolytic cells, an active species such as ozone isefficiently synthesized in a high concentration to yield electrolyticwater having a sterilizing/bleaching ability. The concentration of ozoneor another species in the electrolytic water depends on the amount ofraw water flowing through each chamber per unit time period. The area ofthe section through which raw water flows can be regulated by regulatingthe diameter and number of the rod anode, diameter of the tubularmembrane, and winding pitch of the wire cathode. Thus, electrolyticwater can be efficiently produced.

The method of the invention and the electrolytic-water sprayer of theinvention can be extensively used for the deodorization, sterilization,or bleaching of indoor facilities, water-related facilities, tableware,garments, etc. in the home or for business purposes or for thesterilization or disinfection of the human body, e.g., the hands orfingers, etc. As apparent from the explanations given above, the term“sterilization” in the method of sterilization of the invention meansany of acts such as deodorization, bleaching, and disinfection, besidessterilization.

In the invention, highly active electrolytic water such as the followingcan be yielded by regulating conditions.

(1) Alkaline electrolytic water (alkaline water containing hydrogen gasdissolved therein)

(2) Acid electrolytic water (electrolytic water containing two or moreperoxides yielded by electrolyte selection; sulfuric acid salts,carbonic acid salts, and the like are usable besides chlorides)

(3) High-concentration ozonized water (this water has no residualtendency, has bactericidal activity at least 10 times the bactericidalactivity of hypochlorite systems, and further has a bleaching effect;the ozone half-life is prolonged by some coexistent substances to attainimproved persistency)

(4) Novel composite electrolytic water (having a novel sterilizingeffect brought about by adding an organic acid or surfactant for pHregulation for the purpose of improving bactericidal activity or byadding an alcohol or the like for the purpose of, e.g., improvingbactericidal activity or refreshing feeling)

In the membrane-electrode assembly produced by disposing, in atube-forming manner, a sheet-form ion-exchange membrane or the likearound the periphery of at least one rod electrode and disposing awire-form counter electrode or a porous counter electrode therearound,the rod electrode, membrane, and counter electrode have been unitedtogether. Because of this, the assembly once produced can be easilyhandled. This assembly can be easily produced.

Gas/liquid passages suitable for use as an electrode chamber (or as anelectrode chamber and a counter electrode chamber) are formed byregulating the diameter of the rod electrode, sectional shape of theelectrode, diameter of the tubular membrane and winding pitch in thecase of a wire-form counter electrode, or by selecting the diameter ofthe tube in which those members are disposed to form a counter electrodechamber, and further appropriately deciding the number of the rodelectrode to be used. By changing the water feed rate and current value,the concentration of an electrolytically yielded species in theelectrolytic water can be regulated to a desired value.

The electrolytic water obtained is ejected to or sprayed over asubstance to be sterilized, whereby the substance can be sterilized withthe electrolytically yielded species contained in the desiredconcentration.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view illustrating an electrolytic-water sprayer as oneembodiment of the invention.

FIG. 2 is an exploded enlarged view of an important part of the sprayershown in FIG. 1.

FIG. 3 is a slant view of the electrolytic cell shown in FIGS. 1 and 2.

FIG. 4 is a partial sectional view illustrating another embodiment ofthe electrolytic cell of the invention.

FIG. 5 is a plan view of another rod anode.

FIG. 6 is a plan view of a tubular anode.

FIG. 7 is a partial slant view illustrating a still other embodiment ofthe electrolytic cell of the invention.

FIG. 8 is a transverse sectional view of the electrolytic cell of FIG.7.

The reference numerals used in the drawings denote the following,respectively.

-   -   1: Electrolytic-water sprayer    -   2: Raw water    -   3: Vessel    -   4: Head    -   6, 6 a: Electrolytic cell    -   7, 7 a: Anode    -   8, 8 a: Diaphragm    -   9, 9 a: Wire cathode    -   10, 10 a: Anode chamber    -   15: Vertical pipeline    -   17: Spray nozzle    -   18: Trigger arm    -   22: Trigger-engaged switch    -   32: Electrolytic cell    -   33: Groove    -   34: Anode    -   35: Diaphragm    -   36: Porous cathode    -   37: Anode chamber    -   41: Diaphragm    -   43: Rod anode    -   44: Protrudent part    -   45: Anode chamber    -   46: Diaphragm    -   48: Tubular anode    -   49: Recessed part    -   50: Anode chamber

DETAILED DESCRIPTION OF THE INVENTION

The constituent elements of the invention will be explained below.However, the invention should not be construed as being limited to thefollowing.

Anode and Anode Material:

Examples of anode catalysts for oxidation include lead oxide, tin oxide,noble metals such as platinum, DSAs (electrodes consisting mainly of anoble-metal oxide), carbon, and conductive diamond. From the standpointof corrosion resistance, it is desirable to use as the electrodecatalyst a noble metal such as platinum or iridium, an oxide of such anoble metal, or conductive diamond. The material to be used as anelectrode base preferably has corrosion resistance from the standpointsof attaining a long life and preventing the surface to be treated frombeing fouled. It is desirable to use as the anode base a valve metalsuch as titanium or niobium or an alloy thereof. The anode material canbe deposited on the surface of such a base having a shape heretofore ingeneral use, such as a pipe or rod. Although the sectional shape thereofis desirably selected from circle, quadrangles, ellipses, and the likeor from hollow cylinders, hollow prisms, and the like, it is not limitedto these. To process the surface of a rod-form or cylindrical anode toimpart recesses and protrusions thereto or, in the case of a hollowmaterial, to form openings in the electrode surface is effective inenhancing gas/liquid permeability. A base obtained by rolling a metalgauze into a tubular form is also usable. The height of the recesses andprotrusions is preferably 0.1-5 mm. Also usable is a base having aspiral groove extending in the cylinder direction.

By using a plural number of the anodes, instead of forming the recessesand protrusions on the surface of the anode, it is possible to easilyand assuredly form liquid passages and enhance the gas/liquidpermeability. Specifically, when rod-form or cylindrical anodes arelined up in rows, adjacent anodes are brought into close contact at onepoint and further the contact area of the anodes and the diaphragmdecreases, thereby forming a large space among the anodes and betweenthe anodes and the diaphragm. Therefore, liquid passages (anode chamber)can be formed without requiring troublesome operations such as surfaceprocessing of the anode.

The plural rod-form electrodes may be partly replaced with a memberconsisting of a base having no catalyst formed thereon. In this case,the member plays roles of forming a liquid passage and conducting acurrent to the other rod-form electrode(s).

The presence of a catalyst as part of the anode suffices, and the basemay be partly exposed.

Diamond is regarded as a promising electrode material partly because theelectrical conductivity thereof can be regulated by doping. Diamondelectrodes are inert in water decomposition reaction. It has beenreported that a diamond electrode in oxidation reactions yields ozoneand hydrogen peroxide besides oxygen. When conductive diamond is used,electrolysis reactions proceed more readily and those peroxides asproducts of electrolysis are produced exceedingly efficiently.Furthermore, on the diamond electrode, OH radicals and oxidized forms ofelectrolytes are yielded besides the electrolytically yielded speciesshown above. Consequently, the sterilizing/bleaching effects of the OHradicals or oxidized forms and of the electrolytically yielded speciescan be synergistically utilized.

In the case where conductive diamond is used, examples of usable basesinclude Nb, Ta, Zr, Ti, Mo, W, graphite, and various carbides as well asSi (monocrystalline and polycrystalline). A suitable one can be selectedaccording to applications.

Cathode Material, Cathode Feeder Wire:

Cathode reactions include hydrogen evolution as the main reaction. It istherefore preferred to use an electrode catalyst which is not embrittledby hydrogen. Examples of such preferred electrode catalysts includeplatinum group metals, nickel, stainless steel, titanium, zirconium,gold, silver, carbon, and diamond. As the cathode base, it is desirableto use stainless steel, zirconium, carbon, nickel, titanium, or thelike.

The shape thereof preferably is a wire form. Besides being in a wireform, the cathode may be a metal gauze or foil which has been cutthinly. In the case of a wire form, the cathode may be a windingobtained by twisting plural thin filaments. This form is also preferred.In the case of using a wire cathode, there are cases where this wirecathode functions as a feeder. In the invention, this feeder is includedin the wire cathode.

A porous metal gauze cathode may be rolled into a tubular form anddeposited around the periphery of the ion-exchange membrane or the like.Examples of the porous cathode include expanded meshes and punchingmetals, besides metal gauzes. In the case of using these materials, itis desirable to form recesses and protrusions on the surface of theanode to thereby form an anode chamber between the ion-exchange membraneand the anode. However, an anode chamber may be formed by modifying sucha porous cathode only and partly protruding the diaphragm toward theanode.

A diaphragm, e.g., an ion-exchange membrane, in which a catalyst layerhas been formed beforehand on one side thereof may be disposed so thatthe side having the catalyst faces outward. This constitution ispreferred because the electrolytic cell can have an even currentdistribution and a reduction in cell voltage can hence be attained. Forforming the catalyst layer, existing techniques can be used, such aselectroless plating and PVD. In this case, a metal wire serving also asa feeder is wound thereon. Preferred examples of feeder wire materialsinclude platinum group metals, nickel, iron, copper, silver, gold,stainless steel, titanium, and zirconium.

Diaphragm Material:

As the diaphragm can be used an ion-exchange membrane or a neutralmembrane. Usually, an ion-exchange membrane is used.

A diaphragm not only prevents substances yielded at the anode or cathodefrom being consumed at the opposed electrode, but also has the functionof enabling electrolysis to proceed speedily even when a liquid having alow conductivity is used. Use of a diaphragm is therefore preferred whena raw material having poor conductivity, such as pure water, is used. Inthe case of using an ion-exchange membrane, it may be either afluororesin membrane or a hydrocarbon resin membrane. However, theformer membrane is preferred from the standpoint of resistance tocorrosion by ozone and peroxides. The thickness of the membrane ispreferably 0.1-1 mm.

In the case where a wire cathode is wound on the membrane to form aspiral passage, it is preferred to use as the membrane a commercialmembrane containing reinforcing fibers and having high mechanicalstrength.

It is preferred to form the diaphragm into a tubular shape beforehand.This can be easily accomplished with a precursor resin havingthermoplasticity by a known tube-forming processing technique. Withrespect to the diaphragm, one containing reinforcing fibers ispreferred. Use may be made of a method in which a membrane in a sheetform is rolled into a tube and then bonded. In the case of a fluororesinion-exchange membrane, use can be made of a method in which edge partsof the membrane are superposed and then thermally fusion-bonded togetheror fixed to each other with an adhesive. In the thermal fusion bonding,appropriate ranges of the processing temperature and the areal pressureare 200-350° C. and 2-20 kg/cm², respectively. An appropriate range ofthe processing time period is from 1 second to 1 minute. For increasingbonding strength and attaining more complete bonding, it is preferredthat a narrow strip of a fluororesin membrane containing no reinforcingfibers be interposed in bonding the ion-exchange membrane.

To form recesses and protrusions on the membrane surface is preferredbecause this can enhance gas/liquid permeability.

Membrane-Electrode Assembly:

The length and diameter of the rod anode in the membrane-electrodeassembly are selected according to desired amounts. Usually, the lengththereof is preferably 10-300 mm, and the diameter thereof is preferably0.5-10 mm. The diameter of the diaphragm in the assembly is regulated soas to be larger by about 0.1-5 mm than the diameter of the rod anode(typically supposed to be a cylinder) disposed in the diaphragm.

The percentage of openings of the porous cathode is preferably 20-80%,and the thickness thereof is preferably 0.1-2 mm.

In the case of using a wire cathode (feeder wire), the diameter thereofis preferably in the range of 0.1-2 mm.

In case where the wire cathode is thinner than that, a voltage lossbecomes not negligible due to electrical resistance. Furthermore, such athin cathode is apt to break in a winding operation because the physicalstrength thereof is insufficient. In case where the wire cathode is toothick, the movement of the raw material for electrolysis and products ofelectrolysis from the anode chamber is inhibited, leading to an increasein voltage and a decrease in current efficiency. In addition, such athick cathode is difficult to wind.

In the case where a wire cathode or a feeder wire is spirally wound onthe outer side of the anode and membrane, the wire cathode pitch ispreferably about 0.1-10 mm.

When the wire cathode is spirally wound, the angle of winding isgoverned by the diameter and number of the rod electrode, width of thediaphragm, and diaphragm gap.

The dimensions described above are selected/designed from thestandpoints that even when raw water having low conductivity is used,the electrode is in spiral contact with at least part of the membrane toenable electrolysis to proceed smoothly and that the anode chamberformed by the anode and the membrane needs to have a capacity whichenables the raw water fed and the gas ingredient evolved to flowsmoothly through the anode chamber.

Electrolytic Cell:

At least one of the openings of the anode chamber formed by the anodeand the diaphragm in the membrane-electrode assembly has been fixed to atube connected to a raw-water channel. This tube has almost the samediameter as the tubular diaphragm. The diaphragm and the tube are fixedto each other with an adhesive, and a feeder terminal for the rod anodeis connected to the anode in the tube.

Furthermore, a member obtained by fixing tubes respectively to the twoanode chamber openings of the assembly may be disposed in a second tubewhich has at least two openings and is separated from the member. Thus,a cathode chamber can be newly formed between the second tube and themembrane. A feeder terminal for the wire cathode is connected to thecathode in the second tube.

Raw water is fed to one of the openings of the anode chamber and rawwater is fed also to one of the openings of the cathode chamberaccording to need to conduct electrolysis. By conducting electrolysiswhile feeding raw water to the anode-chamber opening and optionallyfeeding water also to the cathode-chamber opening, electrolytic water isyielded. Thus, alkaline water and acid water can be simultaneouslyyielded according to need.

The inner diameter of the second tube forming the cathode chamber isregulated so as to be larger by about 0.1-5 mm than the diameter of themembrane of the assembly. In case where the second tube is thinner thanthat, substance movement in the catholyte is inhibited and, inparticular, there is a possibility that the deposition of hard-watercomponents from, e.g., tap water might be accelerated. On the otherhand, in case where the second tube is too thick, the catholyte has areduced flow rate and the separation and removal of hard-watercomponents by means of a liquid flow rate becomes impossible. This leadsto an increase in voltage and a decrease in current efficiency. Inaddition, the amount of water stored in the cell increases, making itimpossible to instantaneously obtain alkaline water.

The material of the second tube preferably is a hydrocarbon resin suchas PP, PVC, or PE, a fluororesin, a metal tube, or the like. A tubehaving heat shrinkability is preferred because the capacity of theelectrolytic-cell part can be regulated. The wall thickness of thesecond tube is preferably smaller from the standpoint of rapidlyremoving the heat generated in the electrolytic cell. However, the wallthickness thereof is preferably 0.05-2 mm because mechanical strengthalso is necessary.

The water which is discharged first from the electrolytic cell includesthe raw water which has not been sufficiently electrolyzed. In view ofthis, the amount of the water present in the electrolytic cell and thecapacity of the other parts of the piping preferably are smaller.

It is preferred that the two feeder wires extending from the electrodesshould be covered with an insulating material in order to prevent thewires from coming into contact with each other. It is preferred thateach feeder wire led out of the second tube should be inserted into acovering tube having heat shrinkability and the covering tube befusion-bonded to the wire to thereby isolate the wire from theelectrolytic-water channel in the unit.

In the case of synthesizing ozonized water, too small lengths of thesecond tube extending from the electrolytic cell to the apparatus outletare undesirable because the raw water in which the ozone has notsufficiently dissolved is ejected in this case. The longer thegas/liquid contact time, the more the dissolution of the gaseous ozonein the raw water proceeds and the more the efficiency of the synthesisthereof can be increased. It is therefore preferred that the optimallength be regulated so as to result in a contact time in the range of0.1-10 seconds.

The material of the vessel for storing raw water therein and thematerial of the piping are selected from ones which are not attacked byraw water. The materials may be a PE resin when there is no particularproblem.

With respect to electrolysis conditions, the temperature and the currentdensity preferably are 5-40° C. and 0.01-1 A/cm², respectively, from thestandpoints of the stability and activity of substances yielded.

Raw Water and Electrolytic Water Yielded:

Tap water, well water, or the like can be used as raw water. In thiscase, it is preferred to pass water through the cathode chamber in orderto inhibit the deposition of Ca and Mg. It is also preferred to make theraw water weakly acidic.

Because such water has a low conductivity, there are cases where theresistance loss in the cell voltage is not negligible and it ispreferred to increase the conductivity. In this case, it is preferred todissolve a salt such as Na₂SO₄, K₂SO₄, NaCl, KCl, or Na₂CO₃ as anelectrolyte. There are cases where these salts yield a peroxide uponelectrolysis and thereby impart the persistence of a sterilizing effect.The concentration thereof is preferably in the range of 0.01-10 g/L.Since an electrode such as, e.g., platinum has the property ofincreasing in ozone generation efficiency when chloride ions arepresent, it is preferred to prepare raw water while taking account ofthat property.

When raw water containing metal ions in a large amount, such as tapwater, well water, or seawater, is used, there is a possibility thathydroxides or carbonates might deposit on the surface of the cathode toinhibit reactions. Furthermore, oxides, such as silica, deposit on theanode surface. For eliminating this problem, a reverse current is causedto flow at an appropriate time internal (from 1 minute to 1 hour),whereby acidification and alkalifying occur at the cathode and theanode, respectively. As a result, reactions for removing the depositsreadily proceed while being accelerated by gas evolution and the flow ofthe feed water.

The composition and concentration of the electrolytic water to beyielded can be regulated according to purposes. In the case where theelectrolytic water is intended to be used for food treatment, it shouldbe produced as alkaline electrolytic hypochlorite water, slightly acidelectrolytic water, or ozonized water. However, in the case where theelectrolytic water is intended to be used for sterilization/bleaching, aperoxide may be suitably selected according to the substance to betreated. In the case of hypochlorous acid, the concentration thereof maybe 1-100 ppm. Ozonized water may have a concentration of 1-20 ppm. Theconcentrations of persulfuric acid and percarbonic acid may be 1-100 ppmand 1-100 ppm, respectively.

In the case where hypochlorous acid is to be electrolytically yielded,electrolysis of an acid solution yields hypochlorous acid in a largeramount than a hypochlorite, while use of an alkaline solution yields ahypochlorite in a larger amount than hypochlorous acid. Bactericidalactivity varies depending on the nature of the solution. In general,acid solutions often have higher bactericidal activity than alkalinesolutions. In the control of, in particular, spores and the like, acidsolutions have higher sporicidal activity than alkaline solutions. Incontrast, with respect to fungicidal activity, alkaline solutions aremore active than acid solutions. It is therefore preferred that thenature of the solution should be suitably regulated so as to be acid oralkaline according to the substance to be treated to thereby impartimproved bactericidal or fungicidal activity thereto.

In case where the solution is acidified by adding a strong acid to thesolution to excessively enhance acidity, the hypochlorous aciddecomposes to generate chlorine gas and, as a result, the oxidizingability which brings about the bactericidal activity of hypochlorousacid is impaired. For enhancing the bactericidal activity whilemaintaining the oxidizing ability of the hypochlorous acid, it ispreferred to regulate the solution so as to have a pH of 3-7 at 20° C.For regulating the solution so as to have such a pH, it is preferred touse a water-soluble organic weak acid having a low degree ofdissociation from the standpoint of ease of pH regulation of thesolution. Examples of the water-soluble organic acid include succinicacid, lactic acid, acetic acid, citric acid, and tartaric acid.

For alkalifying the solution, it is preferred to use sodium carbonate,sodium hydrogen carbonate, ammonium carbonate, or the like. Suchcarbonates are oxidized to percarbonic acid by electrolysis.

A surfactant may be added to the solution in order to further improvebactericidal activity. Addition of a surfactant to the solution not onlyimproves the ability of the solution after electrolysis to wet thesubstance to be treated therewith, but also improves the affinity of thesolution for the cell membranes of mold and germs. Thus, thebactericidal or fungicidal effect further improves.

Usable examples of the surfactant include anionic surfactants such asalkylbenzenesulfonic acid salts and polyoxyethylene alkyl ether sulfuricacid salts, cationic surfactants such as benzalkonium chlorides,amphoteric surfactants such as amine oxides (e.g., alkyldimethylamineoxides), and nonionic surfactants such as polyglycerol fatty acid estersand alkylglycosides. The concentration of the surfactant in the solutionis preferably 0.01-10% by weight.

Besides those ingredients, an alcohol may be added to the solution forthe purpose of, e.g., improving bactericidal or fungicidal activity andrefreshing feeling. Furthermore, additives such as, e.g., a perfume,colorant, bactericide other than surfactants, thickener, enzyme,bleaching agent, chelating agent, electrolyte other than chlorinecompounds, builder, antiseptic, and rust preventive may be addedaccording to need. It is especially preferred from the standpoint ofstorage stability that the water to be electrolyzed should contain anantiseptic.

Electrolytic-Water Sprayer (Trigger Spray):

The electrolytic-water sprayer includes a vessel for containing rawwater therein and a head connected to the upper opening of the vessel.Although the vessel may be either rigid or flexible, it is preferredthat the vessel should be made of a rigid material selected from, e.g.,various rigid resins, metals, glasses, and ceramics. The capacity of thevessel is preferably about 10-1,000 mL, more preferably 200-500 mL.

The trigger spray has been fixed to a head in which a battery can behoused. The apparatus may be equipped with a device which generatespower for electrolysis upon trigger operation, without employing abattery as a power source. In place of using a simple primary battery,use may be made of a secondary battery or capacitor, which isrechargeable. It is also possible to operate the apparatus with anadapter capable of supplying DC power from an AC power source.

The values of the voltage and current to be applied are suitablydetermined according to the concentration suitable for obtaining givenbactericidal activity suitable for the substance to be deodorized,sterilized, or otherwise treated and to the volume of the solution to beelectrolyzed. One trigger operation results in the ejection of 0.1-1 cc,and a voltage of about 3-40 V is applied between the electrodes. Adevice for changing the voltage to be applied to the electrodes may bedisposed in the circuit.

A switch for initiating/terminating voltage application to theelectrodes has been disposed in the trigger spray so that a voltage isapplied only when the apparatus is in use, i.e., pulling the triggerautomatically results in switching on and returning the trigger resultsin switching off.

The electrolytic-water sprayer may have a device which generates powerfor electrolysis upon a production operation. Examples of this deviceinclude a motor which interlocks with the trigger. This motor is usuallydisposed in the trigger spray.

The electrolytic-water sprayer can have means for indicating thatelectrolysis is being conducted. Examples of the means include an LEDlamp which is made on during voltage application by a trigger operation.A function may be added which switches off the LED lamp when a specifiedcurrent does not flow due to, e.g., battery exhaustion.

The electrolytic-water sprayer works by the following mechanism. Thesprayer is switched on by a trigger operation to cause a current to flowthrough the circuit. As a result, the current flows through theelectrodes. In this operation, the raw water present in the tube iselectrolyzed almost instantaneously and ejected or sprayed outwardthrough the nozzle of the head by a piston/cylinder mechanism. Namely,in this sprayer of the invention, electrolysis is conductedsimultaneously with a production operation (e.g., trigger operation). Itis preferred that electrolytic water should begin to be yielded byelectrolysis within 1 second after the initiation of a triggeroperation.

Besides the embodiment shown in figures, there are various embodimentsof the electrolytic-water sprayer equipped with a trigger spray.Furthermore, there are trigger sprays having various mechanisms. Thetrigger sprays differ in the liquid passage therein, the position of thefulcrum of the trigger, etc. according to the mechanisms. However, anydesired trigger spray can be employed in the sprayer of the invention.

Next, the electrolytic-water sprayer of the invention is explained withrespect to the embodiment shown in figures. FIG. 1 is a front viewillustrating an electrolytic-water sprayer as one embodiment of theinvention. FIG. 2 is an exploded enlarged view of an important part ofthe sprayer shown in FIG. 1. FIG. 3 is a slant view of the electrolyticcell shown in FIGS. 1 and 2.

The electrolytic-water sprayer (trigger spray) 1 shown in FIG. 1includes a vessel 3 for containing raw water 2 and a head 4 connected tothe upper opening of this vessel 3. The raw water 2 may be pure water ormay be one containing one or more electrolytes dissolved therein, suchas, e.g., sodium chloride, potassium chloride, and magnesium chloride.

In the vessel 3 has been disposed an electrolytic cell 6 composed of ananode, a cathode, and a diaphragm. As shown in FIG. 2, this electrolysiscell 6 is constituted of; an anode 7 which is a metallic rod electrodeon which a catalyst has been deposited; a diaphragm 8 which is a tubularion-exchange membrane wound around the anode 7; and a wire cathode 9which is a metallic wire wound around the diaphragm 8. This diaphragm 8is obtained by rolling a square sheet so as to have a circular shapewhen viewed from above and bonding two end parts along the lengthwisedirection.

The diaphragm 8 intrinsically has no recesses/protrusions. However, bywinding the wire cathode 9 on the diaphragm 8, that part of thediaphragm 8 which is in contact with the wire cathode 9 is stronglypushed against the anode 7, and that part of the diaphragm 8 which isnot in contact with the wire cathode 9 is bent outward to form a spiralanode chamber 10 between the anode 7 and the diaphragm 8.

Furthermore, that space in the vessel 3 which is on the outer side ofthe diaphragm 8 constitutes a cathode chamber.

A tube for feeder wire holding 13 has been connected to the upper end ofthe rod anode 7 through a cylindrical connecting tube 12 having a shortlength. A feeder wire 14 is held between the inner surface of theconnecting tube 12 and the outer surface of the tube for feeder wireholding 13, and an end of the feeder wire 14 has been connected to anupper end part of the anode 7.

The upper end of the tube for feeder wire holding 13 has been fittedinto a vertical pipeline 15 in the head 4, and the upper end of thevertical pipeline 15 is communicatively connected to a horizontalpipeline 16 in the head 4.

At the other end of the horizontal pipeline 16 has been disposed a spraynozzle 17. A fulcrum 19 of a trigger arm 18 has been disposed on theslightly inner side of the spray nozzle 17 so that the trigger arm isswingably movable around the fulcrum 19. The trigger arm 18 has beenconnected to a piston rod 20 extending inward so that the piston rod 20travels in a cylinder 21 according to the movement of the trigger arm18.

Numeral 22 denotes a trigger-engaged switch disposed so as to be incontact with the trigger arm 18; 23 denotes a power source batterydisposed in the head 4; and 24 denotes an LED which is on only whenelectrolysis is proceeding.

The electrolytic-water sprayer 1 having such constitution is held in ahand, and an inward force is applied to the trigger arm 18 with theforefinger and middle finger. As a result, the trigger arm 18 movesaround the fulcrum 19, whereby the trigger-engaged switch 22 becomes onand a voltage is applied to the electrolytic cell 6. Simultaneouslytherewith, the piston in the cylinder 21 moves to bring the raw water 2present in the vessel 3 into contact with the electrolytic cell 6, wherethis raw water 2 is electrolyzed to yield electrolytic water. The anode7 in this electrolytic cell 6 has a catalyst, such as, e.g., a layer ofconductive diamond, deposited on the surface thereof. Thus, electrolyticwater containing ozone or other active species dissolved therein in ahigh concentration is obtained. Since a spiral anode chamber 10 has beenformed inside the diaphragm 8 in this electrolytic cell 6, anappropriate gas/liquid passage is formed in the anode chamber.Consequently, the concentration of an electrolytically yielded speciesin the electrolytic water can be regulated to a desired value bychanging the water feed rate and current value.

The electrolytic water yielded passes instantaneously through thevertical pipeline 15 and horizontal pipeline 16 and is sprayed throughthe spray nozzle 17 on a substance to be sterilized, together with airintroduced through an outside-air intake opening not shown.

FIG. 4 is a partial sectional view illustrating another electrolyticcell according to the invention. This figure shows an embodimentemploying a porous cathode and an anode to which recesses andprotrusions have been imparted.

The electrolytic cell 32 is constituted of an anode (rod electrode), acathode (counter electrode), and a diaphragm. This electrolytic cell 32is composed of: an anode 34 which is a metallic rod electrode having aspiral groove 33 formed in the periphery thereof; a diaphragm 35 whichis an ion-exchange membrane formed into a tubular shape and disposedaround the periphery of the anode 34; and a porous cathode 36 having theshape of a metal gauze, expanded mesh, or punching metal and disposedaround the periphery of the diaphragm 35.

Unlike the embodiment shown in FIGS. 1 to 3, this embodiment issubstantially free from deformation of the diaphragm 35 toward the anode34 by the porous cathode 36. However, since the anode 34 has a groove 33formed in the periphery thereof, this embodiment has an anode chamber 37formed between that part of the diaphragm 35 which corresponds to thegroove 33 and the anode 34.

In this embodiment also, an appropriate gas/liquid passage is formed inthe anode chamber, and the concentration of an electrolytically yieldedspecies in the electrolytic water can be regulated to a desired value bychanging the water feed rate and current value.

The embodiment in which the anode has recesses and protrusions shouldnot be construed as being limited to that having the groove. Althoughthe embodiment explained above employs a rod-form or tubular anodehaving a circular shape when viewed from above, the shape of the anodeis not limited thereto. For example, the anode may have shapes such asthose shown by the plan views in FIGS. 5 and 6.

The diaphragm 41 in FIG. 5 has a vertically tubular form obtained byrolling a square sheet and bonding overlap parts 42 of the two ends toeach other. The rod anode 43 has protrudent parts 44 projected outwardrespectively in six parts of the base in a solid cylinder form. Thetubular diaphragm 41 has been stretched on and around the six protrudentparts 44. Six anode chambers 45 in total have been thus formed betweenthe diaphragm 41 and the anode 43.

In the case of FIG. 6 also, the diaphragm 46 has a vertically tubularform obtained by rolling a square sheet and bonding overlap parts 47 ofthe two ends to each other. The tubular anode 48 has a shape obtainedfrom a prismatic base by forming a recessed part 49 depressed inward ateach of the four corners. The tubular diaphragm 46 has been stretched onand around a total of eight base parts of the four recessed parts 49.Anode chambers 50 corresponding to the shapes of the recessed parts 49are formed between the diaphragm 46 and the anode 48.

FIG. 7 is a partial slant view illustrating a still other embodiment ofthe electrolytic cell of the invention, and FIG. 8 is a transversesectional view of the electrolytic cell of FIG. 7. This embodimentrelates to an improvement of the embodiment shown in FIGS. 1 to 3, andexplanation of common members will be omitted by assigning the samereference numerals.

In the electrolytic cell 6 a shown in FIGS. 7 and 8, two rods of anodesmade of niobium and covered with a conductive-diamond catalyst on thesurface thereof are wrapped by an ion-exchange membrane 8 a so as toform two layers of the membrane in tubular form, and a stainless wireserving as a cathode 9 a is spirally wound on the membrane to therebyform an anodes-membrane-cathode assembly (electrolytic cell).

According to this embodiment, as shown in FIG. 8, the anodes 7 a are inrod-form, and a relatively large space is formed between the two anodes7 a each having a curved surface. In addition, a relatively large spaceis also formed between the anodes 7 a and the ion-exchange membrane 8 a.These spaces function as an anode chamber 10 a, and electrolytic waterpasses through this anode chamber 10 a.

According to this embodiment, cost- and time-consuming processing of theanode per se is not required unlike the embodiment as shown in FIGS. 4to 6. Despite that, this embodiment provides an anode chamber having avolume equal to or rather larger than that in the embodiment of FIGS. 4to 6.

EXAMPLES

Examples concerning the production of electrolytic water according tothe invention will be given below. However, the invention should not beconstrued as being limited to the following Examples. The ozoneconcentration, hypochlorous acid concentration, persulfuric acidconcentration, and percarbonic acid concentration in each Example weredetermined with an ultraviolet spectrophotometer and by iodometry usingpotassium iodide.

Example 1

A rod made of niobium (diameter, 2 mm) on which a conductive-diamondcatalyst (dopant boron concentration, 2,500 ppm) had been deposited wasplaced as an anode in a tubular ion-exchange membrane (Nafion 350,manufactured by DuPont; thickness, 0.35 mm; diameter, 3 mm). Acommercial platinum wire (diameter, 0.4 mm) was spirally wound as acathode on the diaphragm to obtain an anode-membrane-cathode assembly.The winding pitch was 4 mm. Tubes (diameter, 4 mm) were bonded to upperand lower parts of the assembly, and feeder wires from a DC power sourcewere connected to the respective electrodes to obtain an electrolyticcell. Pure water was passed upward through the anode chamber at a rateof 40 cc/min. Currents of 0.5 A and 1 A were separately caused to flow.As a result, the cell voltages were 13 V and 19 V, respectively, theozonized water concentrations were 8 ppm and 21 ppm, respectively, andthe ozone generation efficiencies were 13% and 12%, respectively, inthese operations. The temperature of the water at the outlet was about30° C.

This electrolytic cell was connected in a trigger type sprayer shown inFIG. 1 to a PE resin tube attached to the intake. A battery was mountedin the head of the trigger type sprayer. In a circuit part, theelectrode terminals were connected to a variable resistor and a switchwith a wiring. The vessel was filled with 500 cc of pure water.

The trigger was pulled, upon which the circuit was switched on and acurrent flowed between the battery and the cell. Simultaneouslytherewith, pure water was ejected. The amount of the pure water ejectedwas about 0.5 cc, and the quantity of electricity which flowed duringthis operation was 0.25 C (0.5 s×0.5 A). The terminal voltage of thecell was 13 V. The operation was repeatedly conducted 100 times. As aresult, the ozone concentration in the solution ejected, which amountedto about 50 cc, was 8 ppm. The trigger operation was repeated 2,000times, and the concentration of the ozonized water obtained thereafterremained at about 8 ppm.

Comparative Example 1

The same materials as in Example 1 were used. A strip of theion-exchange membrane was spirally wound on the anode, and the platinumwire was wound on the diaphragm to obtain an anode-membrane-cathodeassembly. Pure water was passed upward at a rate of 40 cc/min through anelectrolytic cell in which the membrane-electrode assembly had beenmounted. Currents of 0.5 A and 1 A were separately caused to flow. As aresult, the oxygen and ozone generated at the anode were mixed with thehydrogen gas generated at the cathode because the diaphragm had beendisposed spirally, and electrolytic water containing these gasesdissolved therein was yielded. In these operations, the cell voltageswere 10 V and 13 V, respectively, the ozonized water concentrations were5 ppm and 9 ppm, respectively, and the ozone generation efficiencieswere 8% and 5%, respectively.

Example 2

Those parts of the membrane in the assembly of Example 1 whichconstituted the two openings of the anode chamber were fixed to tubeshaving a diameter of 4 mm. The resultant member was disposed in a secondtube having an inner diameter of 5 mm to form a cathode chamber betweenthe second tube and the membrane. A feeder terminal for the wire cathodewas connected to the cathode in the second tube. A 2 g/L aqueoussolution of sodium chloride was fed to the anode chamber at a rate of 40cc/min, and water was fed also to the cathode chamber in the samemanner. A current of 1 A was caused to flow. As a result, alkaline watercontaining hydrogen and having a pH of 11 and acid water containinghypochlorite ions in an amount of 40 ppm could be simultaneouslyyielded.

Example 3

The same test as in Example 2 was conducted, except that tap water wasfed to the anode chamber and the cathode chamber. As a result, theozonized water yielded at 0.5 A had a concentration of 4.5 ppm (currentefficiency, 7.3%).

Comparative Example 2

The same test as in Comparative Example 1 was conducted, except that tapwater was used as a raw material. As a result, the ozonized wateryielded at 0.5 A had a concentration of 1.5 ppm (current efficiency,2.4%).

Example 4

A round rod made of titanium which had a platinum layer formed thereon(20 g/m²) was used as an anode to produce the same assembly as inExample 1. Using tap water as a raw material, the same test as inExample 3 was conducted. As a result, the cell voltage at 0.5 A was 12V, and the ozonized water had a concentration of 0.5 ppm.

Example 5

Two rods made of niobium (diameter, 2 mm) on which a conductive-diamondcatalyst had been deposited (dopant boron concentration, 1,000 ppm) asanodes were wrapped by an ion-exchange membrane (Nation 324,manufactured by DuPont; thickness, 0.35 mm; diameter, 3 mm) so as toform two layers of the membrane in tubular form, and a stainless wire(diameter, 0.5 mm) serving as a cathode is spirally wound on themembrane to thereby obtain an anodes-membrane-cathode assembly as shownin FIGS. 7 and 8. The winding pitch was 2 mm.

Tubes (diameter, 4 mm) were bonded to upper and lower parts of theassembly, and feeder wires from a DC power source were connected to therespective electrodes to obtain an electrolytic cell. Pure water waspassed upward through the anode chamber at a rate of 40 cc/min. Currentsof 0.5 A and 1 A were separately caused to flow. As a result, the cellvoltages were 13 V and 19 V, respectively, the ozonized waterconcentrations were 15 ppm and 17 ppm, respectively, and the ozonegeneration efficiencies were 13% and 15%, respectively, in theseoperations. The temperature of the water at the outlet was about 30° C.Water leakage from the tubular membrane scarcely occurred.

While the present invention has been described in detail and withreference to specific embodiments thereof, it will be apparent to oneskilled in the art that various changes and modifications can be madetherein without departing from the spirit and scope thereof.

This application is based on Japanese Patent Application Nos.2007-296769 (filed Nov. 15, 2007) and (filed Oct. 15, 2008), and thecontents thereof are herein incorporated by reference.

1. A membrane-electrode assembly which comprises: at least one rod-formor tubular electrode; a tubular diaphragm disposed around the peripheryof the electrode; and a wire-form counter electrode disposed around theperiphery of the diaphragm, the diaphragm being fixed to the rod-form ortubular electrode with the wire-form counter electrode to thereby forman electrode chamber having a gas/liquid passage between the diaphragmand the rod-form or tubular electrode.
 2. The membrane-electrodeassembly of claim 1, comprising a plurality of rod-form or tubularelectrodes.
 3. The membrane-electrode assembly of claim 1, wherein thewire-form counter electrode is spirally wound at a pitch of 1-10 mm. 4.A membrane-electrode assembly which comprises: at least one rod-form ortubular electrode; a tubular diaphragm disposed around the periphery ofthe electrode; and a porous counter electrode disposed around theperiphery of the diaphragm, the diaphragm being fixed to the rod-form ortubular electrode with the porous counter electrode to thereby form anelectrode chamber having a gas/liquid passage between the diaphragm andthe rod-form or tubular electrode.
 5. A membrane-electrode assemblywhich comprises: at least one rod-form or tubular electrode having arecessed part formed therein; a tubular diaphragm disposed around theperiphery of the electrode so as to form an electrode chamber having agas/liquid passage between the diaphragm and the electrode; and a platycounter electrode disposed around the periphery of the diaphragm.
 6. Themembrane-electrode assembly of any one of claims 1 to 5, wherein therod-form or tubular electrode comprises diamond.
 7. Themembrane-electrode assembly of any one of claims 1 to 5, wherein therod-form or tubular electrode is an anode and the counter electrode is acathode.
 8. An electrolytic cell which comprises: the membrane-electrodeassembly of any one of claims 1 to 5; a feeder wire-fixing tube fittedto at least one of openings of the electrode chamber of the assembly;and a feeder wire fixed between the opening and the feeder wire-fixingtube.
 9. An electrolytic cell which comprises: the membrane-electrodeassembly of any one of claims 1 to 5; and a tube for forming a tubularcounter electrode chamber, the tube being disposed around the electrodechamber and the counter electrode.
 10. The electrolytic cell of claim 8,which yields electrolytic water, the electrolytic water comprisingozonized water as a main component.
 11. The electrolytic cell of claim9, which yields electrolytic water, the electrolytic water comprisingozonized water as a main component.
 12. An electrolytic-water sprayerwhich comprises: the electrolytic cell of any one of claims 8 to 11; avessel containing raw water; and a head, wherein the raw water iselectrolyzed with the electrolytic cell and the electrolytic water thusyielded is ejected from the head.
 13. A method of sterilization withelectrolytic water which comprises: yielding electrolytic water with theelectrolytic-water sprayer of claim 11; and ejecting the resultantelectrolytic water to a substance to be sterilized.